The proposed research is aimed at supplying basic information about mechanisms of sensory processing invertebrates. These studies will exploit a specialized lower vertebrate sensory system, the electrosensory system of gymnotoid fish. Single neuron responses will be studied in all of the brain areas known to process electrosensory information while behaviorally relevant stimuli are presented to the animal. The main questions that I hope these studies will help answer are: 1) "What sorts of changes in acuity or resolution occur as information received over the electric sense is passed through the processing hierarchy?" 2) "Are regions of the central nervous system specialized to process information of a given modality only during specific behavioral situations and/or do the details of this processing change as a function of the behavioral situation?" 3) "To what extent is information received via the electric sense integrated with that received over other sensory systems in various brain areas?" Known aspects of the animals' behavior will influence stimulus design and data evaluation and behavioral experiments are planned in collaboration with an ethologist currently studying these same animals. These studies will estimate the contribution of various brain areas to quantifiable behaviors. The electrosensory system is phylogenetically related to the auditory system of higher vertebrates therefore the proposed studies will not only contribute to our understanding of basic mechanisms of vertebrate sensory processing but they may also contribute to our understanding of the neurophysiology of audition.